Livestock Research for Rural Development 4 (2) 1992

Citation of this paper

Molasses-urea block (MUB) and Acacia mangium as supplements for crossbred heifers fed poor quality forages

Bui Xuan An, Ngo Van Man, Luu Trong Hieu

University of Agriculture and Forestry, HoChiMinh City, VietNam


In the first experiment, twenty four crossbred heifers, given forages of low nutritive value, were divided equally into 4 groups with different supplements: C1, 1 kg/d concentrate; MUB, 1 kg/d concentrate + 0.5 kg/d MUB; AM, 1 kg/d concentrate + fresh Acacia mangium leaves (2 kg/100 kg LW); AMMUB, 0.5 kg/d MUB + fresh Acacia mangium leaves (2 kg/100 kg LW). The experiment period was 90 days. DM intakes were 5.08, 6.21, 5.61, and 5.49 kg/d, and live weight gains were: 107, 340, 185, 236 g/d, for treatments C, MUB, AM and AMUB, respectively.

In experiment 2 a rumen-fistulated cow was fed 3 diets in turn: C, rice straw; MUB, rice straw + 0.5 kg/d MUB; AM rice, straw + fresh Acacia mangium leaves (2kg/100 kg LW). Rate of disappearance of rice straw increased 16-17% with MUB supplementation. There was no apparent effect of the Acacia mangium leaves.

KEY WORDS: Rice straw, Acacia mangium, rumen in sacco digestibility, rumen ecosystem, cattle, molasses-urea, blocks, growth


The basal diet of most of the cattle and buffaloes in Vietnam is based on agro-industrial residues, roadside grass or grazing on boundaries between crops. These diets are imbalanced in nutritional value and variable according to seasons.

In order to develop a sustainable ruminant production system in Vietnam, efforts are directed to making the best use of local feed resources by adjusting the production system according to the local conditions. The use of appropriate supplements is a fundamental component of the feeding strategy in order to balance nutrients at the level of the rumen and of the animal (Preston and Leng 1987).

The multi-nutritional block (MUB) based on molasses and urea is being introduced and used in many Asian countries (Leng and Preston 1983). It is easy to make, of low cost, uses local resources and is safe to feed.

Acacia mangium, a leguminous tree, has been planted on thousands of hectares in Vietnam. It produces abundant foliage especially in the dry season (Ngo and Nguyen 1991).

The aim of this study was to determine:

# The effect on performance of growing crossbred cattle of using MUB and Acacia mangium leaves as supplements to a basal diet derived, according to availability, from native grasses, sugarcane tops, guinea grass silage and rice straw given ad libitum.

# The effects of the supplements on the rumen ecosystem as measured by the rates of degradability of standard fibre sources.

Materials and methods

Experiment 1

24 crossbred Holstein-Sindhi heifers (170 kg liveweight, 18-21 months of age) were divided into four treatment groups and fed the same basal diet (native grasses and molasses given in restricted amounts; sugarcane tops, guinea grass silage and rice straw given ad libitum, according to availability). The experimental period was 90 days in the dry season. The treatments were:

C: 1 kg/d concentrate mixture
MUB: 1 kg/d concentrate + 0.5 kg/d MUB
AM: 1 kg/d concentrate + 2 kg/100 kg liveweight of fresh Acacia mangium leaves
AMMUB: 0.5 kg/d MUB + 2 kg/100 kg liveweight of Acacia mangium leaves


The Acacia mangium leaves were harvested by hand, wilted in the shade for 24 hr then chopped into 10-15 cm pieces before feeding to the animals (NB: Acceptance of the fresh leaves was low, but improved when the leaves were wilted for 24hr). The chemical composition (AOAC 1970) of the MUB is shown in Table 1 and of the rest of the feed resources in Table 2. The cattle were weighed every 14 days and records kept of feed intake.

Experiment 2

A Sindi-local breed (Chinese yellow) heifer of 226 kg liveweight and 30 months of age was fitted with a rumen cannula. It was given the following three diets in consecutive periods of 14 days, the measurements of degradability in the rumen of standard fibre sources being made over the last 2 days of each period.

RS: Rice straw ad libitum
RSMUB: Rice straw ad libitum + 0.5 kg/d MUB (10% urea)
AM: Rice straw ad libitum + 2 kg/100 kg liveweight of fresh Acacia mangium leaves

The chemical composition of the straw and Acacia leaves is given in table 3.

Rice straw was used as the test feed to determine the efficacy of the rumen ecosystem to digest dry matter, organic matter and fibre. The nylon bag technique described by Orskov et al (1980) was used. There were four replicates of rice straw during the incubation for each of the three diets fed to the host animal.


Table1: Composition (%) of the MUB used in the two experiments
  Ingredients Exp.1 Exp.2
  Urea 10 10
  Molasses 35 35
  Rice bran 29 -
  Peanut husks - 30
  Lime 10 9
  Bentonite 10 10
  Salt 5 5
  Trace minerals 1 1


Table 2: Checmical composition of feeds used in experiment 1

% in DM

Feed DM N x 6.25 Crude fibre
Sugarcane tops 39.0 6.99 37.1
Native grasses 36.1 8.57 37.0
Guinea grass silage 53.6 4.8 42.5
Rice straw 53.7 5.84 39.9
Molasses 69.3 5.59 0.23
Concentrate 92.0 16.5 12.1
Acacia foliage 29.7 17.5 44.8


Table 3: Chemical composition of the feeds used in experiment 2
Feed DM     % in DM  
    N x 6.25 Fibre E Extract Ash
Rice straw 87.7 4.06 50.1 1.06 10.9
Acacia leaves 30.0 16.7 55.3 5.97 4.82


Results and discussion

Experiment 1

There was an indication that intake of the basal feed (the low- nutritive value component of the diet) was higher when MUB was given. Only some 65% of the amounts offered of Acacia mangium leaves was consumed.


Table 4: Feed dry matter intakes in experiment 1
Feed DM intake,kg/d          
Basal feed 4.19 4.96 4.07 4.63  
Total diet 5.08 6.21 5.61 5.49  


Table 5: Mean value for liveweights and gains in experiment 1
Initial 169 170 170 169  
Final 179 201 186 291  
Gain/day* 109 340 185 237 ±24(.001)

* Adjusted by covariance for initial weight.

The MUB increased significantly the growth rate when concentrates were the only supplement, and the combination of MUB and Acacia mangium was better than that of concentrates alone or the combination of concentrates and Acacia mangium. This strongly indicates that (i) there was a deficiency of rumen ammonia when the basal diet was composed of grasses, cane tops and rice straw; and (ii) the unsuitability of the concentrate supplement (90% rice bran and 5% fish meal) for supplying ammonia for rumen microorganisms. The consistent positive effect of the MUB supplement on feed intake and on liveweight gain confirms many reports in the literature which indicate the value of this type of supplement when the basic diet is low in nitrogen (Leng and Preston 1984; Preston and Leng 1987; Sansoucy 1986).

The better results from the combination of MUB and Acacia mangium leaves than from concentrates justifies the strategy of supplementing the microbes (with MUB) and the animal (with the Acacia leaves).

Experiment 2

The rates of degradability of dry matter, organic matter and crude fibre in the rice straw test feed were increased by supplementing the rice straw diet of the host animal with MUB. There was no apparent effect of the Acacia mangium leaves.

Table 6: Mean values for degradability of rice straw in the rumen of a fistulated heifer fed rice straw, straw + MUB and straw + Acacia mangium leaves
  DM OM Crude fibre
Degradability in 48h      
Rice straw      
Mean 41.29 39.00 46.96
SE ±2.4 ±2.4 ±2.8
Rice straw +MUB      
Mean 47.9 45.7 54.9
SE ±3.2 ±2.5 ±2.8
Rice straw + Acacia mangium leaves      
Mean 42.6 46.0 51.2
SE ±1.4 ±1.3 ±2.2


The results with MUB are similar to those reported by Perdok and Leng (1990). There are data in the literature, for similar basal diets, indicating beneficial effects on rumen fibre degradability when supplements of fresh grass (Guttierrez and Elliott 1981) or leucaena leaves were given. The fact that this was not observed in experiment 2 may be because of the low rumen degradability of both the dry matter and the nitrogen in fresh Acacia mangium leaves (Bui et al 1992).


As a supplement to rice straw for growing heifers, the combination of MUB and Acacia mangium leaves was better than that of concentrates or the combination of concentrates and Acacia mangium. This strongly indicates that (i) there was a deficiency of rumen ammonia when the basal diet was composed of grasses, cane tops and rice straw; and (ii) the unsuitability of the concentrate supplement (90% rice bran and 5% fish meal) for supplying ammonia for rumen microorganisms.


The authors acknowledge the financial support received from the TCP/FAO project and the SAREC project S/2 Vie 22. They are also highly appreciative of the co-operation of people of AnPhuoc state farm, farmers in GoVap district, SongBe Animal Husbandry Union and students of the Animal Husbandry and Veterinary Medicine Faculty of UAF.


AOAC 1970 Official Methods of Analysis, 6th edition. Association of Official Analytical Chemists, Washington, DC

Bui A X, Luu H T, Duong K N and Preston T R 1992 Effect of position in the tree and pretreatment of Acacia mangium leaves on rumen dry matter and nitrogen degradabilities. Livestock Research for Rural Development. Volume 4, Number 2

Guttierrez E, Elliott R and Harrison D 1981 The effect of the supplement of African Star Grass on the digestibility of cellulose and rumen kinetics in male lambs receiving a basal diet of henequen pulp. Tropical Animal Production 6:361

Kabatanga M A and Shayo C M 1991 Degradation of maize stover as influenced by leucaena hay supplementation. Livestock Research for Rural Development Volume 3, Number 2:19-22

Leng R A 1984 The potential of solidified molasses-bases block for the correction of nutritional deficiencies. In buffaloes and other ruminants fed low quality agro-industrial by-products. Use of nuclear technique to improve domestic buffalo production in Asia. (IAEA:Vienna)

Leng R A and Preston T R 1983 Nutritional strategies for the utilisation of agro industrial by-products by ruminants and extension of the principles and technologies to the small farmers in Asia. In ±Proceedings the 5th World Conference on Animal Production±. Volume 1: 310-318

Ngo V M and Nguyen V H 1991 Effect of spacing on growth and yield of legume trees on low fertility grey soils in south eastern Vietnam. In: Proceedings of International Symposium on Increasing Livestock Production by Making Better Use of Local Resources in Vietnam (Editors: L V Ly, H T Luu, B Ogle and T R Preston). FAO; Bangkok (In press)

Orskov E R, Hovell F D DeB and Mould F 1980 The use of the nylon bag technique for the evaluation of feedstuffs. Tropical Animal Production 5:195-213

Perdok H B and Leng R A 1990 Effect of supplementation with protein meal on the growth of cattle given a basal diet of untreated or ammoniated rice straw. Asian-Australasian Journal of Animal Sciences 3: 269-279

Preston T R and Leng R A 1987 Matching Ruminant Production Systems with Available Resources in the Tropics and Subtropics. PENAMBUL Books Ltd: Armidale NSW, Australia

Sansoucy R 1986 The Sahel: Manufacture of molasses-urea blocks. World Animal Review 57:40-48

(Received 16 July 1992)